1. Field of the Invention
The present invention relates to a fuse-fetching circuit, and more particularly, to a highly cost-effective fuse-fetching circuit.
2. Description of the Related Art
Fuses have been widely used in memory devices or consumer product integrated circuits (ICs) to store operations of a semiconductor component. For example, ID fuses are embedded in memory devices or consumer product ICs to record the manufacturing process, such as wafer lot number, positions on the X-axis and Y-axis of the wafer from which the dies of the memory devices or consumer product IC come. Another common practice is that if memory devices install internal recovery circuits, the fuses are used to record (melted and blown by a laser) the locations of defective memory cells. Since there are usually more ID fuses than the output pins of a semiconductor component upon a test mode, serial output from a single or a few pins is commonly seen. After the supply voltage is switched on, the fuse information is read one by one through the single or a few pins.
U.S. Pat. No. 6,215,351 discloses a traditional fuse-latch circuit, which needs additional delay element and latch element to store or control the fuse information, and thus its hardware is costly. U.S. Pat. No. 7,091,564 discloses another traditional fuse-fetching circuit. Please refer to FIG. 1. A fuse unit 10 includes a fuse 11, a latch circuit 12 and a transfer circuit 13, and many fuse units 10 are repeated and arranged in a row to form a fuse unit group. Signals bBP, AN and bTR are used to control or initiate the fuse unit 10. Before the latch information is read, the signal bBP is initiated to reset the latch 12. Then the signal AN is turned on to load the content of the fuse 11 into the latch 12. Next, the signal bTR is initiated to load the content of the latch 12 into the transfer circuit 13. Following each transition of the shifting clock, the fuse information is captured by an external controller. Although the fuse unit 10 can complete the fuse-fetch tasks, its hardware is too costly. Because the structure of the fuse unit 10 is replicated repeatedly to form the fuse unit group, it is necessary to develop a more cost-effective structure of the fuse unit 10 to save the space in the chip area.